A typical cellular wireless network includes a number of base stations that radiate to define wireless coverage areas, such as cells and cell sectors, in which wireless client devices (WCDs) such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly equipped devices, can operate. Each base station may then be coupled with network infrastructure that provides connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or the Internet for instance. With this arrangement, a WCD within coverage of the cellular wireless network may engage in air interface communication with a base station and may thereby communicate via the base station with various remote network entities or with other WCDs served by the base station.
Such a network could operate in accordance with a particular air interface protocol, with communications from the base stations to WCDs defining a downlink and communications from the WCDs to the base stations defining an uplink. Examples of existing air interface protocols include, without limitation, Long Term Evolution (LTE) (using Orthogonal Frequency Division Multiple Access (OFDMA) on the downlink and Single Carrier Frequency Division Multiple Access (SC-FDMA) on the uplink), Code Division Multiple Access (CDMA) (e.g., 1×RTT and 1×EV-DO), Global System for Mobile Communications (GSM), and Wi-Fi, among others. Each technology may define its own procedures for managing communications with WCDs.
In accordance with the air interface protocol, each coverage area could operate on a carrier (carrier frequency), which could be frequency division duplex (FDD) or time division duplex (TDD). An FDD carrier would use separate frequency channels for downlink and uplink communication, whereas a TDD carrier would use a single frequency channel multiplexed over time between downlink and uplink use. In either case, the downlink and uplink would each typically span a particular frequency bandwidth, defining within the frequency bandwidth various air interface resources for carrying communications between the base station and served WCDs. Further, the air interface resources could be grouped or otherwise structured to define various logical channels for carrying control signaling and bearer traffic (e.g., application-layer traffic) between the base station and WCDs.
When a base station serves WCDs in such an arrangement, the base station could coordinate transmission of data over the air between the base station and the WCDs. For instance, when the base station receives data destined to a WCD, the base station could select downlink air interface resources to carry the data and could coordinate transmission of the data over the air to the WCD within those resources. And when a WCD has data to transmit, the WCD could send a scheduling request to the base station, and the base station could responsively select uplink air interface resources to carry the data and could coordinate transmission of the data over the air from the WCD within those resources.